Wireless power transmitter and receiver for vehicle

ABSTRACT

According to an embodiment of present invention, a wireless power transmitter for a vehicle that transfers power to a wireless power receiver includes: a coil assembly comprising first and second bottom coils placed adjacent to each other in a line and each consisting of a single layer of 11 turns and a top coil stacked on the first and second bottom coils and consisting of a single layer of 12 turns; and a full-bridge inverter driving each of the coils included in the coil assembly individually, wherein the first and second bottom coils and the top coil have a substantially rectangular frame structure with a through hole in the center, the top coil lies on a plane surface in the middle between the first and second bottom coils, and a distance from the center of the first and second bottom coils to the center of the top coil is set to a range of 23 mm to 25 mm.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is the National Phase of PCT International ApplicationNo. PCT/KR2016/012682, filed on Nov. 4, 2016, which claims priorityunder 35 U.S.C. 119(e) to U.S. Provisional Application No. 62/251,118,filed on Nov. 5, 2015, all of which are hereby expressly incorporated byreference into the present application.

TECHNICAL FIELD

The present invention relates to a structure for a wireless powertransmitter and receiver for a vehicle and a method for controlling thesame.

BACKGROUND ART

A contactless wireless charging method is an energy transfer method forelectromagnetically transferring energy without using a wire in a methodfor sending energy through an existing wire so that the energy is usedas power for an electronic device. The contactless wireless transmissionmethod includes an electromagnetic induction method and a resonantmethod. In the electromagnetic induction method, a power transmissionunit generates a magnetic field through a power transmission coil (i.e.,a primary coil), and a power reception coil (i.e., a secondary coil) isplaced at the location where an electric current may be induced so thatpower is transferred. In the resonant method, energy is transmittedusing a resonant phenomenon between the transmission coil and thereception coil. In this case, a system is configured so that the primarycoil and the secondary coil have the same resonant frequency, andresonant mode energy coupling between the transmission and receptioncoils is used.

DISCLOSURE Technical Problem

The present invention provides a novel coil assembly structure for awireless power transmitter for a vehicle that has good chargingefficiency/performance, and a method of operating such a wireless powertransmitter for a vehicle.

Technical Solution

An embodiment of the present invention provides a wireless powertransmitter for a vehicle that transfers power to a wireless powerreceiver, including: a coil assembly comprising first and second bottomcoils placed adjacent to each other in a line and each consisting of asingle layer of 11 turns and a top coil stacked on the first and secondbottom coils and consisting of a single layer of 12 turns; and afull-bridge inverter driving each of coils included in the coil assemblyindividually, wherein the first and second bottom coils and the top coilhave a substantially rectangular frame structure with a through hole inthe center, the top coil lies on a plane surface in the middle betweenthe first and second bottom coils, and a distance from the center of thefirst and second bottom coils to the center of the top coil is set to arange of 23 mm to 25 mm.

Also, a level of power transferred to the wireless power receiver by thecoil assembly may be controlled based on a level of input voltageapplied to the full-bridge inverter.

Also, the level of voltage applied to the full-bridge inverter may beadjusted within a range of 1 V to 18 V.

Also, an operating frequency of the coil assembly may be fixed within arange of 140 to 150 kHz.

Also, the first and second bottom coils may have a height of 48 mm to 50mm and a width of 47 mm to 49 mm, and the through hole in the first andsecond bottom coils may have a height and width of 18 mm to 20 mm.

Also, the top coil may have a height of 45 mm to 47 mm and a width of48.5 mm to 50.5 mm, and the through hole in the first and second coilsmay have a height of 20 mm to 22 mm and a width of 24.5 mm to 26.5 mm.

Also, a thickness of the first and second bottom coils and the top coilmay be set to a range of 0.9 mm to 1.3 mm.

Also, the first and second bottom coils and the top coil may have thesame inductance value.

Also, the first and second bottom coils and the top coil may have thesame inductance value within a range of 10.6 μH to 12.0 μH.

Technical Effects

According to an embodiment of the present invention, the application ofa multi-coil driving scheme to a coil assembly widens the chargeablearea but minimizes the unchargeable area, thereby increasing thecharging performance/efficiency.

Also, according to an embodiment of the present invention, it ispossible to prevent frequency interference with other electronicparts/equipment within the vehicle as the power transmitter operates ata fixed operating frequency.

Also, according to an embodiment of the present invention, the powertransmitter has a very wide adjustable input voltage range of 1 V to 18V, and supports high input voltage, thus increasing the z distance d_zand enabling long-distance charging. This gives vehicle manufacturers agreater degree of freedom in the installation of a power transmitter ina vehicle.

Other advantages of embodiments of the present invention will bedescribed below in detail.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows an embodiment of various electronic devices into which awireless charging system is introduced.

FIG. 2 is a block diagram of a wireless power transmission/receptionsystem in accordance with an embodiment of the present invention.

FIG. 3 is a block diagram of a power transmitter in accordance with anembodiment of the present invention.

FIG. 4 is a diagram illustrating a coil assembly structure for a powertransmitter in accordance with an embodiment of the present invention.

FIG. 5 illustrates a coil structure in accordance with an embodiment ofthe present invention.

FIG. 6 is a diagram illustrating a shielding structure that covers acoil assembly in accordance with an embodiment of the present invention.

FIG. 7 is a diagram illustrating an equivalent circuit of a powertransmitter in accordance with an embodiment of the present invention.

FIGS. 8 and 9 show test results of the power transfer performance of apower transmitter designed in accordance with an embodiment of thepresent invention.

FIGS. 10 and 11 show test results of the transmit power level adjustmentfunction of a power transmitter designed in accordance with anembodiment of the present invention.

FIGS. 12 and 13 show test results of the thermal performance of a powertransmitter designed in accordance with an embodiment of the presentinvention.

BEST MODE FOR INVENTION

Terms used in this specification are common terms which are now widelyused by taking into consideration functions in this specification, butthe terms may be changed depending on an intention of those skilled inthe art, a use practice, or the appearance of a new technology.Furthermore, in a specific case, some terms have been randomly selectedby the applicant. In this case, the meaning of a corresponding term isdescribed in a corresponding part of a corresponding embodiment.Accordingly, the terms used in this specification should not beunderstood simply based on their names, but should be understood basedon their substantial meanings and contents over this specification.

Furthermore, although embodiments of the present invention are describedin detail with reference to the accompanying drawings and contentsdescribed in the drawings, the present invention is not limited to orrestricted by the embodiments.

Hereinafter, some embodiments of the present invention are described indetail with reference to the accompanying drawings.

For the standardization of wireless power transmitter/receivers,Wireless Power Consortium (WPC) standardizes technologies related towireless power transmission/reception.

A recently developed wireless charging system may support thetransmission/reception of low power of about 5 W. In this case, there isa problem in that a charging time is long and efficiency is low in sucha low power charging method because the size of a mobile device and thecapacity of a battery are recently increased. Accordingly, a wirelesscharging system supporting the transmission/reception of middle power ofabout 15 W˜20 W is developed. Furthermore, in order to improve chargingefficiency, a wireless charging system to which a resonant method forsimultaneously charging a plurality of electronic devices has been addedis developed.

An embodiment of the present invention relates to a wireless chargingsystem to which the resonant method has been added and proposes awireless charging transmitter/receiver using the resonant method, whichis compatible with a wireless charging transmitter/receiver using anelectromagnetic induction method supporting low power/middle power.

A wireless power transmitter and wireless power receiver of a resonanttype proposed by an embodiment of the present invention and a wirelesscharging method and a communication protocol using the wireless powertransmitter and wireless power receiver are described below.Furthermore, a wireless power transmitter may be abbreviated as a powertransmitter or a transmitter, and a wireless power receiver may beabbreviated as a power receiver or a receiver.

FIG. 1 shows an embodiment of various electronic devices into which awireless charging system is introduced.

FIG. 1 shows that electronic devices are classified depending on anamount of power that is transmitted and received in a wireless chargingsystem.

Referring to FIG. 1, a small power (about 5 W or less or about 20 W orless) wireless charging method may be applied to wearable devices, suchas a smart watch, smart glass, a head mounted display (HMD), and a smartring, and mobile electronic devices (or portable electronic devices),such as an earphone, a remote controller, a smart phone, a PDA, and atablet PC. A middle power (about 50 W or less or about 200 W or less)wireless charging method may be applied to middle/small-sized homeappliances, such as a notebook computer, a robot clearer, a TV, an audioequipment, a vacuum and a monitor. A large power (about 2 kW or less or22 kW or less) wireless charging method may be applied to kitchenequipment, such as a mixer, a microwave, and an electric rice cooker,and personal mobile devices (or electronic devices/mobile means), suchas a wheel chair, an electric kickboard, an electric bicycle, and anelectric vehicle.

Each of the aforementioned electronic devices/mobile means (or shown inFIG. 1) may include a wireless power receiver to be described later.Accordingly, the aforementioned electronic devices/mobile means may bewirelessly charged with power received from a wireless powertransmitter.

Hereinafter, a mobile device to which the small wireless charging methodis applied is chiefly described for convenience of description, but thisis only an embodiment. A wireless charging method in accordance with anembodiment of the present invention may be applied to the aforementionedvarious electronic devices.

FIG. 2 is a block diagram of a wireless power transmission/receptionsystem in accordance with an embodiment of the present invention.

Referring to FIG. 2, a wireless power transmission/reception system 2000includes a mobile device 2010 configured to wirelessly receive power anda base station 2020 configured to wirelessly transfer (or transmit)power. Hereinafter, the mobile device may also be called a “powerreceiver product”, and the base station may also be called a “powertransmitter product.”

The mobile device 2010 includes a power receiver 2011 for wirelesslyreceiving power through a secondary coil and a load 2012 for receivingpower received by the power receiver 2011, storing the received power,and supplying the stored power to a device.

The power receiver 2011 may include a power pick-up unit 2013 and acommunications & control unit 2014. The power pick-up unit 2013 mayreceive a wireless power signal through the secondary coil and convertthe received signal into electric energy. The communications & controlunit 2014 may control the transmission/reception of a power signal (orpower).

The base station 2020 is a device for providing inductive power orresonant power, and may include at least one power transmitter 2021 or asystem unit 2024.

The power transmitter 2021 may send inductive power or resonant powerand control such transmission. The power transmitter 2021 may include apower conversion unit 2022 configured to convert electric energy into apower signal by generating a magnetic field through a primary coil(s)and a communications & control unit 2023 configured to controlcommunication and power transfer with the power receiver 2011 so thatpower of a proper level is transferred. The system unit 2024 may performcontrol of other operations of the base station 2020, such as inputpower provisioning, control of a plurality of power transmitters, andcontrol of a user interface.

The power transmitter 2021 may control transmission power by controllingan operating point. The controlled operating point may correspond to acombination of a frequency (or phase), a duty cycle, a duty ratio, andvoltage amplitude. The power transmitter 2021 may control transmissionpower by controlling at least one of a frequency (or phase), a dutycycle, a duty ratio, or voltage amplitude.

Furthermore, the power transmitter 2021 may supply constant power, andthe power receiver 2011 may control reception power by controlling aresonant frequency.

In this specification, a (primary/secondary) coil or a coil unit mayalso be called a coil assembly, a coil cell, or a cell which includes acoil and at least one element close to the coil.

FIG. 3 is a block diagram of a power transmitter in accordance with anembodiment of the present invention.

Referring to FIG. 3, the power transmitter 3000 may include two mainunits: a power conversion unit 3020 and a communications & control unit3010. The power conversion unit 3020 may perform communication with thecommunications & control unit 3010.

The power conversion unit 3020 may be in charge of/include the analogpart of a power transmitter design. The power conversion unit 3020 mayinclude an inverter, a primary coil selection block, and/or a currentsense unit. The power conversion unit 3020 (or inverter) may receive DC(direct current) input and convert it to an AC waveform for operating aresonant circuit including a series capacitor and a primary coil(s).Here, the primary coil may refer to a coil that is appropriatelyselected from among at least one coil in the power transmitter dependingon the location of the power receiver, in order to charge the powerreceiver.

The power conversion unit 3020 (or coil selection block) may select atleast one coil in a proper position to charge the power receiver, fromamong the coils included in a coil assembly, depending on the locationof the power receiver placed on the coil assembly.

Coil selection may be done/performed in real time by the powertransmitter 3000 (or power conversion unit 3020/coil selection block) byperforming/attempting communication with the power receiver using atleast one coil included in the coil assembly (or all the coils insequence). That is, the power transmitter 3000 (or power conversion unit3020/coil selection block) may find the location of the power receiverby performing communication with the power receiver using at least onecoil, and may select one coil corresponding to the location of the powerreceiver,

For example, the power transmitter 3000 (or power conversion unit3020/coil selection block) may attempt communication with the powerreceiver using at least one coil included in the coil assembly, and itcan be assumed that an attempt to communicate with the power receiverusing the first coil among them has succeeded. In this case, the powertransmitter 3000 (or power conversion unit 3020/coil selection block)may determine/predict that the power receiver is currently placed on thefirst coil (or closest to the first coil), and may select the first coilas a coil to be driven for charging the power receiver.

Alternatively, although not shown in the drawing, the power transmitter3000 may have a separate sensor (e.g., a proximity sensor, infraredsensor, etc.) for finding the location of the power receiver. In thiscase, the power transmitter 3000 may find the location of the powerreceiver by using the corresponding sensor, and may select a coil in aproper position to charge the power receiver as a drive coil.

Lastly, the power conversion unit 3020 (or current sense unit) maycontinuously monitor the current flowing through a selected coil.

The communications & control unit 3010 may be in charge of/include thedigital logic part of a power transmitter design including a coilassembly.

More specifically, the communications & control unit 3010 may receiveand decode a message from the power receiver, constitute a coilselection block to connect with a proper coil, and execute a powercontrol algorithm/protocol related to the coil selection block.Moreover, the communications & control unit 3010 may control/drive thefrequency of an AC waveform for controlling power transfer. In addition,the communications & control unit 3010 may interface with othersubsystems of the base station (for the purpose of user interfacing, forexample).

Although this block diagram shows and describes the power conversionunit 3000 and the communications & control unit 3010 separately, thepresent invention is not limited to this and at least one of thefunctions of the power conversion unit 3000 may be performed by thecommunications & control unit 3010 or at least one of the functions ofthe communications & control unit 3010 may be performed by the powerconversion unit 3000. Furthermore, the power conversion unit 3000 andthe communications & control unit 3010 may be configured as separatechips or built into one chip.

So far, the block diagram of the power transmitter 3000 in accordancewith an embodiment of the present invention has been described. Below isa description of a coil assembly structure that may be included in thepower transmitter 3000.

FIG. 4 is a diagram illustrating a coil assembly structure for a powertransmitter in accordance with an embodiment of the present invention.

Referring to FIG. 4, the coil assembly for a power transmitter inaccordance with an embodiment of the present invention may include threecoils. Each of the three coils may have a substantially rectangularframe structure with a through hole in the center.

The coil assembly may include two bottom coils (or referred to as“bottom primary coils”) arrayed and placed in a line and a top coil (orreferred to as “top primary coil”) placed on (or over) the bottom coils.In other words, the coil assembly may have a stack structure of aplurality of coils stacked on a plane surface to overlap, with thebottom coils being arranged on a first layer, and the top coil beingstacked on the first layer.

If one of the two bottom coils included in the coil assembly is referredto as a first bottom coil and the other as a second bottom coil, thedistance d_12 from the center of the first bottom coil to the center ofthe second bottom coil may be about 46±4 mm. The top coil may be placedorthogonal to the bottom coils, and may lie in the middle between thetwo bottom coils arrayed in a line. The distance d_bt from the center ofthe first and/or second bottom coil to the center of the top coil may beabout 23±2 mm. Although not shown in this drawing, the distance d_z fromthe top surface of the coil assembly (or the top surface of the topcoil) to the interface surface of the base station may be about 5.5±1.5mm. Here, the interface surface may refer to a flat surface closest tothe primary coils, among a plurality of surfaces constituting the basestation, or refer to a flat surface closest to the secondary coil, amongthe surfaces of the mobile device. The self inductance L_p of each coil(or primary coil) may be about 11.3±0.7 μH.

The following is a more detailed description of a structure of each ofthe coils (or primary coils—i.e., the bottom coils and the top coil)constituting the coil assembly proposed in this specification.

FIG. 5 illustrates a coil structure in accordance with an embodiment ofthe present invention. Specifically, FIG. 5(a) is a diagram illustratinga bottom coil structure, and FIG. 5(b) is a diagram illustrating a topcoil structure. Hereinafter (or in this specification), the bottom coiland the top coil will be commonly referred to as “primary coils” forconvenience of explanation.

The primary coils may be wire-wound type, and may consist of a 17 AWG(American wire gauge) litz wire made from 105 strands of 40 AWG wire(0.08 mm in diameter), or a litz wire of similar type or structure. Aspreviously described, the primary coils may include two types ofrectangular coils (bottom coil and top coil), and each coil may consistof a single layer. Each primary coil may be designed to have the sameinductance value so as to be independent from the distance from ferrite.

The bottom coil may be placed close to the ferrite in the powertransmitter, and the bottom coil may have specific parameter values aspresented in the table shown in FIG. 5(a).

Referring to the table shown in (a) of FIG. 5, the bottom coil may bedesigned to have an outer length (or outer height) d_ol of about49.0±1.0 mm, an inner length (or inner height) d_il of about 26.0±1.0 mm(or about 19.0±1.0 mm), an outer width d_ow of about 44.0±1.0 mm (orabout 48.0±1.0 mm), an inner width d_iw of about 22.0±1.0 mm (or about19.0±1.0 mm), and a thickness d_c of about 1.1±0.2 mm. The bottom coilmay be designed to have a single-layer structure, and the number N ofturns per layer in the bottom coil may be 11.

The top coil may be placed close to the interface of the powertransmitter, and the top coil may have specific parameter values aspresented in the table shown in FIG. 5(b).

Referring to the table shown in FIG. 5(b), the top coil may be designedto have an outer length (or outer height) d_ol of about 46.0±1.0 mm, aninner length (or inner height) d_il of about 21.0±1.0 mm, an outer widthd_ow of about 49.5±1.0 mm, an inner width d_iw of about 25.5±1.0 mm, anda thickness d_c of about 1.1±0.2 mm. The top coil may be designed tohave a single-layer structure, and the number N of turns per layer inthe top coil may be 12.

FIG. 6 is a diagram illustrating a shielding structure that covers acoil assembly in accordance with an embodiment of the present invention.

Referring to FIG. 6, a soft magnetic material may protect and cover thebase station from magnetic fields generated by the primary coils. Theshielding may extend a minimum of 2 mm beyond the outer edges of theprimary coils and be a minimum of 2 mm thick. The shielding may beprovided below the primary coils and have a distance d_s of maximum 1.0mm from the primary coils. The shielding may be made of manganese-zinc(MnZn) ferrite (e.g., PM12 of Todaisu).

The distance d_z (or z distance) from the top face of the primary coilsto the interface surface of the base station may be about 1.1±0.2 mm.The interface surface of the base station may be designed to extend aminimum of 5 mm beyond the outer edges of the primary coils.

FIG. 7 is a diagram illustrating an equivalent circuit of a powertransmitter in accordance with an embodiment of the present invention.

Referring to FIG. 7, the power transmitter (or coil assembly drivecircuit) in accordance with an embodiment of the present invention mayuse/include a full-bridge inverter (hereinafter, abbreviated as“inverter”) for driving individual primary coils and a series capacitorC_p. This full-bridge inverter concept may correspond to theabove-described power conversion unit or be included in it.

The coil assembly and the shielding may be designed to have a magneticinductance L_p of about 11.3±0.7 μH (i.e., 10.6˜12.0 μH), and the seriescapacitor C_p may be designed to have a capacitance of about 139±6% pH(i.e., 133˜147 nF).

The power transmitter (or communications & control unit) may control theinput voltage applied to the inverter in order to control the amount ofpower transmitted to the power receiver. More particularly, the powertransmitter (or communications & control unit) may control the inputvoltage applied to the inverter over the range of 1 V to 18 V, with aresolution of 10 mV. The inverter may operate in mid-power mode andlow-power mode. The operating frequency f_op of the power transmitter(or coil assembly) may be substantially fixed at about 140 to 150 kHz,with a duty cycle of 50%. As used herein, the operating frequency maymean the oscillation frequency of a voltage/power signal applied todrive/operate the power transmitter (or coil assembly). An externalvoltage applied to the power transmitter may range from 10 V to 14 V(generally, 12 V).

In a case where the power transmitter (or communications & control unit)transmits/applies a power signal (e.g., digital ping signal), an initialvoltage of about 5.0±0.5 V may be used to the bottom and top coils, andthe operating frequency used may be in the range of 140 kHz to 150kHz—for example, 145 kHz.

Control of the power transmitter (or communications & control unit) maybe performed using a proportional integral differential (PID) algorithm.As used herein, the PID algorithm (or PID controller) denotes analgorithm that basically takes the form of a feedback controller,calculates an error value by measuring an output value of an objectintended to be controlled and comparing the measured output value to areference value or setpoint, and derives a control value required byusing the error value.

To ensure accurate power control, the power transmitter (orcommunications & control unit) may determine the amplitude of primarycell current (same as primary coil current) with a resolution of about 7mA.

Tables 1 and 2 below show parameter values that may be used in the TIDalgorithm.

TABLE 1 Parameter Symbol Value Unit Proportional gain Krp 10 mA⁻¹Integral gain Kri 1 mA⁻¹ ms⁻¹ Derivative gain Krd 0 mA⁻¹ ms Integralterm upper limit Mriu 3000 N.A. Integral term lower limit Mril −3000N.A. PID output upper limit Mrupid 20000 N.A. PID output upper limitMrlpid −20000 N.A. PID Scaling Factor Krpid 100 N.A

TABLE 2 Parameter Symbol Value Unit Proportional gain Kdp 30 mA⁻¹Integral gain Kdi 1 mA⁻¹ ms⁻¹ Derivative gain Kdd 0 mA⁻¹ ms Integralterm upper limit Mdiu 3000 N.A. Integral term lower limit Mdil −3000N.A. PID output upper limit Mdupid 20000 N.A. PID output upper limitMdlpid −20000 N.A. PID Scaling Factor Kdpid 15 N.A

With all of the above considered, the power transmitter (or a powertransmitter circuit or the communications & control unit) in accordancewith an exemplary embodiment of the present invention may control thepower transferred to the power receiver by controlling the input voltageapplied to the inverter. In this case, a substantially fixed operatingfrequency, adjustable only in the range of about 140 kHz to 150 kHz, maybe used. The adjustable input voltage range is 1 V to 18 V, which ismuch wider than the range of input voltage applied to the inverter fromother power transmitters. With this feature, the power transmitter ofthis invention has the following advantages and effects when used as awireless power transmitter for a vehicle.

One of the advantages is that it is possible to prevent frequencyinterference with other electronic parts/equipment within the vehicle asthe power transmitter operates at a fixed operating frequency. Frequencyinterference between the power transmitter and other electronicparts/equipment may cause safety issues critical for the driver's lifeand safety. Accordingly, unlike other general power transmitters, apower transmitter for a vehicle proposed in this invention may regulatethe transferred power by controlling the input voltage instead of theoperating frequency.

Another advantage is that the power transmitter has a very wideadjustable input voltage range of 1 V to 18 V, and supports high inputvoltage, thus increasing the z distance d_z and enabling long-distancecharging. This gives vehicle manufacturers a greater degree of freedomin the installation of a power transmitter in a vehicle.

As such, the power transmitter designed as shown in FIGS. 4 to 7 may bemade and used as a low-power transmitter for a vehicle that enableslow-power charging at about 5 W or as a medium-power transmitter for avehicle that enables wireless power charging at about 15 W.

Now, test results of the power transfer performance of the powertransmitter designed as shown in FIGS. 4 to 7 will be discussed.

FIGS. 8 and 9 show test results of the power transfer performance of apower transmitter designed in accordance with an embodiment of thepresent invention.

In the test of FIGS. 8 and 9, the power transmitter transferred power tothe power receiver, aiming at reaching six target voltage levels a˜f,and actual measurements of the voltage received by the power receiverwere made. The target voltage levels for power transfer to the powerreceiver were set as follows:

-   -   a: 4.2V, b: 7.0V, c: 4.2V, d: 7.5V, e: 5.0V, f: 5.0V

From the Guaranteed Power category of FIG. 8, it is demonstrated thatthe power transfer performance test results were pass for all the sixtarget voltage levels a˜f. More specifically, referring to FIGS. 9(a) to9(f), it is demonstrated that power was transferred to the powerreceiver at appropriate voltage levels, without a large deviation fromthe target voltage levels.

Besides, referring to FIG. 8, it is demonstrated that the powertransmitter of the invention satisfies all the power transmitterspecifications defined by the WPC standard.

FIGS. 10 and 11 show test results of the transmit power level adjustmentfunction of a power transmitter designed in accordance with anembodiment of the present invention.

More specifically, FIG. 10(a), FIG. 10(b), FIG. 11(a), and FIG. 11(b)show test results of the transmit power level adjustment function of thepower transmitter when the target power level is 8 W, 15 W, 12 W, and 15W, respectively. In FIGS. 10 and 11, a “Sent Control Error: n” messageindicates that the power currently received by the power receiver is n Wless than the target transmit power.

Referring to the test results of FIGS. 10 and 11, the power transmitterof this invention may find out how far the current level of power beingtransferred to the power receiver falls below the target power level byperforming communication with the power receiver, and based on this, mayadjust the transmit power level to the target power level. That is, thetest results of FIGS. 10 and 11 reveal that the power transmitter ofthis invention may adjust the transmit power level to the target powerlevel by performing proper communication with the power receiver.

FIGS. 12 and 13 show test results of the thermal performance of a powertransmitter designed in accordance with an embodiment of the presentinvention.

More specifically, FIG. 12 shows test results from measurements oftemperature changes in a foreign object (FO) when a power transmitterdesigned in accordance with an embodiment of the present inventiontransfers low power (about 5 W) to the FO, rather than the powerreceiver. FIG. 13 shows test results from measurements of temperaturechanges in the power receiver when the power transmitter transfers lowpower to the power receiver.

Referring to FIG. 12, it is demonstrated that the FO temperature did notgo up or it increased up to 49□. Referring to FIG. 13, it isdemonstrated that the temperature of the power receiver increased up to32□.

From these test results, it can be said that the power receiver or FOthat receives power from the power transmitter does not rise above aspecific temperature, and this allows the user to use the powertransmitter of this invention without risk of explosion or fire.

Furthermore, the drawings have been divided and described forconvenience convenience of description, but the embodiments describedwith reference to the drawings may be merged and designed to implementnew embodiments. Furthermore, the display device is not limited andapplied to the configurations and methods of the aforementionedembodiments, but some or all of the embodiments may be selectivelycombined and configured so that the embodiments are modified in variousways.

Furthermore, although some embodiments of this specification have beenillustrated and described, this specification is not limited to theaforementioned specific embodiments and may be modified in various waysby those skilled in the art to which this specification pertains withoutdeparting from the gist of this specification claimed in the claims. Themodified embodiments should not be individually interpreted from thetechnical spirit or prospect of this specification.

Mode for Invention

Various embodiments have been described in the best mode for invention.

INDUSTRIAL APPLICABILITY

The present invention may be applicable to various wireless chargingtechnologies.

The invention claimed is:
 1. A wireless power transmitter that transferspower to a wireless power receiver, comprising: a coil assemblycomprising first and second bottom coils placed adjacent to each otherin a line and each consisting of a single layer of 11 turns and a topcoil stacked on the first and second bottom coils and consisting of asingle layer of 12 turns; and a full-bridge inverter driving each coilincluded in the coil assembly individually, wherein the first and secondbottom coils and the top coil have a substantially rectangular framestructure with a through hole in the center, wherein the top coil lieson a plane surface in the middle between the first and second bottomcoils, wherein a distance from the center of the first and second bottomcoils to the center of the top coil is set to a range of 21 mm to 25 mm,wherein the first and second bottom coils have a height of 48 mm to 50mm and a width of 43 mm to 45 mm, and the through hole in the first andsecond bottom coils has a height of 25 mm to 27 mm and a width of 21 mmto 23 mm, wherein the top coil has a height of 45 mm to 47 mm and awidth of 48.5 mm to 50.5 mm, and the through hole in the top coil has aheight of 20 mm to 22 mm and a width of 24.5 mm to 26.5 mm, and whereinthe first and second bottom coils and the top coil have a thickness of0.9 mm to 1.3 mm.
 2. The wireless power transmitter of claim 1, whereina level of power transferred to the wireless power receiver by the coilassembly is controlled based on a level of input voltage applied to thefull-bridge inverter.
 3. The wireless power transmitter of claim 2,wherein the level of voltage applied to the full-bridge inverter isadjusted within a range of 1 V to 18 V.
 4. The wireless powertransmitter of claim 2, wherein an operating frequency of power signalstransmitted from the wireless power transmitter is fixed within a rangeof 140 kHz to 150 kHz.
 5. The wireless power transmitter of claim 1,wherein the first and second bottom coils and the top coil have a sameinductance value within a range of 10.6 μH to 12.0 μH.